1. Field of the Invention
The present invention relates to a coordinate detecting apparatus for detecting a coordinate position on a screen of an optical projector, and, more particularly, to a coordinate detecting apparatus of the above type for detecting as a coordinate position information of a picture image on the screen.
2. Description of the Prior Art
An optical projector is an apparatus, in which a portion which is desired by an observer is selected from either a picture image recorded on a film sheet or the like or an object to be observed and then is enlarged and projected on a screen for easy observation. Thus, the present invention is directed to a coordinate detecting apparatus for an optical projector, in which information of a picture image enlarged and projected by the optical projector on a screen which is intended by an observer to be transmitted to an outside processing system such a an electronic computer is directly indicated by the observer on the screen using a light pen so that the particular information can be detected as a coordinate position to be converted into an output signal for indicating the digital coordinate position.
Heretofore, a variety of coordinate detecting apparatuses for a CRT display device have been proposed and some of them have been put into actual practice. However, few coordinate detecting apparatuses have been proposed for an optical projector. Although it is possible to convert some of the coordinate detecting apparatuses for a CRT display device, other than those the type using a light pen resorting to the raster of the CRT, into a coordinate detecting apparatus for an optical projector by making some suitable changes including the use of an ultrasonic pen, a Rand tablet or the like, some special devices on the screen are required resulting in problems including a reduction in economy and picture quality.